Heretofore, asphalt compositions have been widely used in applications such as road pavement, waterproof sheets, sound isolation sheets, and roofings. In this respect, many attempts have been made to improve the properties of asphalt by adding various polymers to the asphalt.
For example, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, rubber latexes, and block copolymers consisting of conjugated diene and vinyl aromatic hydrocarbon are used as the polymers.
In recent years, there has been a growing demand for asphalt compositions having excellent strength and abrasion resistance associated with circumstances such as increase in the number of vehicles passing through roads or their speedup. This requires a higher softening point and mechanical strength such as elongation and modulus. Thus, attempts have been made to improve these properties, for example, by increasing the molecular weights of block copolymers for use as the polymers mentioned above. Such a method, however, tends to deteriorate workability.
Therefore, attempts have generally been made to raise the softening points of asphalt compositions by adding an aromatic oil or by performing cross-linking by the addition of sulfur or peroxide.
For example, Patent Document 1 discloses use of a binder containing a sulfur-donating compound.
Patent Document 2 discloses an asphalt composition containing a copolymer consisting of conjugated diene having a specific structure and vinyl aromatic hydrocarbon.
Patent Document 3 discloses an asphalt composition for roofing singles containing a block copolymer consisting of vinyl aromatic hydrocarbon and conjugated diene, and a filler.
Patent Document 4 discloses an asphalt composition containing a copolymer consisting of conjugated diene having a specific structure and vinyl aromatic hydrocarbon.